Runner in flawed research without oxygen (9)
I believe the answer is:
racehorse
'runner' is the definition.
(a racehorse runs races)
'flawed research without oxygen' is the wordplay.
'flawed' is an anagram indicator (I've seen this in other clues).
'without' is an insertion indicator ('without' can be similar in meaning to 'outside').
'oxygen' becomes 'O' (atomic symbol for oxygen).
'research' with letters rearranged gives 'racehrse'.
'racehrse' going around 'o' is 'RACEHORSE'.
'in' is the link.
(Other definitions for racehorse that I've seen before include "jumper?" , "runner" , "Steeplechaser, maybe" , "Which a jockey rides" , "Animal" .)